Ceramic Coatings and Glass Additives for Improved SiC-Based Filters for Molten Iron Filtration



Reticulated silicon carbide (SiC) ceramic filters are prepared with modified coatings in an attempt to improve mechanical properties of the sintered filter. Two classes of coatings are used: mixtures of non-SiC ceramic and sintering aid and mixtures of SiC and glass. Various candidate ceramics, sintering aids, and glasses are screened. The most promising coatings are determined to be silica with 5 wt% bismuth oxide and SiC with ≤10 wt% Spruce Pine Batch glass. Filters with these coatings are prepared and subjected to mechanical abuse. Both coatings improve the ruggedness of the filter relative to the standard uncoated SiC type. Filters with <10 wt% glass additive were subjected to molten metal impingement and filtration of liquid gray iron at 1510°C. Those with 5 wt% glass or more softened during filtration. Those with 2.5 wt% glass or less survived without failure.